The present invention relates to a motor vehicle lock for all types of motor vehicle doors, hoods or flap locks and the like.
Today's motor vehicle locks typically have the locking elements lock catch and locking pawl arranged such that the lock catch interacts with a striker, mounted on the vehicle body, when the vehicle door is closed. The lock catch can be held by the locking pawl in a main locking position or (if available) a preliminary position when the locking pawl is in its lowered position. The lock catch has for that purpose a main locking element, and, if available, a preliminary locking element, which can be brought into engagement with a locking nose mounted on the locking pawl. Through raising the locking pawl, the lock catch is released towards its opening position. Typically, the lock catch is biased towards its opening position, whereas the locking pawl is biased towards its locked position.
For a smooth opening process it must be ensured that the locking pawl remains in the raised position until the preliminary locking element of the locking pawl has passed the locking nose of the locking pawl. If the locking pawl falls back into its lowered position too early, the locking nose of the locking pawl engages with the preliminary locking element or even with the main locking element so that the opening process is interrupted or does not start at all. Such a situation may arise if the shifting of the lock catch into the opening position is briefly obstructed, for example, because of ice buildup on the vehicle door or the vehicle tailgate being loaded with the weight of a layer of snow.
To avoid the above described interruption of the opening process, it is known from German patent application DE 195 20 359 A1 to provide a motor vehicle lock with a memory function. The memory function ensures that the locking pawl remains, during the opening process, in its raised position until the preliminary locking element of the lock catch has passed the locking nose of the locking pawl. For this purpose, the motor vehicle lock has a lever-shaped memory element typically referred to as the “snow weight lever”. During the raising of the locking pawl, the memory element falls from a raised into a lowered position and thereby holds the locking pawl in its raised position. During the course of the opening process, the lock catch shifting towards its opening position presses the memory element into its raised position so that the locking pawl is ultimately released due to the forced coupling between the lock catch and the memory element. The known motor vehicle lock has an opening motor drive through which the locking pawl can be raised by means of a motor.
A similar concept is implemented in the motor vehicle lock described in German patent application DE 196 17 428 A1. Here, too, a lever-shaped memory element is provided, which is assigned to the locking pawl and keeps the locking pawl in the raised position as described above. Further, an opening motor drive is provided that interacts on the one hand with the locking pawl and on the other hand with the memory element. In addition, a pre-locking suppression system is provided, which, however, does not play a role here.
Finally, a motor vehicle lock with a memory function is known from European patent EP 0 978 610 B1 as having an elastic, lever-shaped memory element which is rigidly coupled to the locking pawl. During the raising of the locking pawl, the memory element snaps into engagement with the lock catch and, hence, keeps the locking pawl in the raised position. During the shifting of the lock catch towards its opening position the snap-on connection opens and the locking pawl is released.
It should be noted that the above-described memory function not only leads to an increase in the convenience of use, but can under certain circumstances be essential for the operation of the motor vehicle lock. By way of example, a further known motor vehicle lock (from German patent application DE 102 34 782 A1) is provided with an opening motor drive. During the opening process, the opening motor drive shifts the locking pawl initially into the raised position and then runs off block to a stop arranged on the locking pawl. The stop is in the path of the opening drive only if the locking pawl is raised. It needs to be ensured that the locking pawl remains raised until the blocking of the opening drive—which corresponds to the above-described memory function.
In all of the above described motor vehicle locks, the memory element holds the locking pawl, while in the memory state, in a raised position until the lock catch reaches its opening position. Hence, the locking pawl remains in the raised position even if the vehicle door cannot be opened due for example to the aforementioned icing. If such an obstruction should later and/or suddenly disappear, as may be the case due to melting, the vehicle door will open unexpectedly. Such unwanted behavior of the system poses a substantial accident risk.